The Great HIIT debate
cutmd
Posts: 1,168 Member
For interested parties, here is a good article for hiit and a good article saying hiit isn't better than steady state cardio. Why should we care? If hiit really burns way more fat than steady state, then all of us who are fit enough should be doing it. On the other hand, hiit is HARD, who wants to put themselves through it for the same result a longer, milder session would yield?
So what do you think? It seems to me there must be some distinction the body makes between 200 calories burned walking and 200 calories burned during insanity because of how spent the latter leaves me...
FOR HIIT (from http://www.cbass.com/FATBURN.HTM)
From The Desk of Clarence Bass
FORGET THE FAT-BURN ZONE
High Intensity Aerobics Amazingly Effective
"The rate of increase in V02max is one of the highest ever reported."
Izumi Tabata, Japan
"Fat burn is greater when exercise intensity is high." Metabolism
I believe in high-intensity aerobics. In Ripped 3, for bodybuilders, I recommended "a variety of relatively short and infrequent aerobic sessions interspersed with explosive muscular effort." In Lean For Life, published six years later, I emphasized high-intensity aerobics even more; I reduced the frequency of aerobic sessions to two times a week (in Ripped 3 I recommended up to four) and substantially increased the intensity. But it wasn't until recently, when my friend Richard Winett, Ph.D., publisher of Master Trainer, called my attention to new research findings, that I came to fully appreciate the superiority of high intensity aerobics compared to the usual prescription that heart rate be maintained between 60% and 80% of maximum.
As explained in the nearby FAQ (Low intensity aerobics?), high intensity aerobics burns the same amount of fat as low intensity, but the expenditure of calories is substantially greater; plus, intense aerobics produces a higher level of fitness. Importantly, the more fit you become, the more likely you are to use fat as fuel for any given activity. And now, research in Japan and in Canada shows that short, very intense aerobic sessions are amazingly effective for both fitness and fat loss.
Maximal oxygen uptake, or V02max, is generally regarded as the best single measure of aerobic fitness. As the rate of exercise increases, your body eventually reaches a limit for oxygen consumption. This limit is the peak of your aerobic capacity, or your V02max. As intensity increases beyond V02max, your body must shift to anaerobic (without oxygen) energy production. An oxygen debt begins to build at this point and blood lactate levels climb. In general terms, one's ability to continue exercising in the face of rising oxygen deficit and lactate levels is called anaerobic capacity.
This is important because many high-intensity sports (including basketball, football, soccer and speed skating) require a high level of both aerobic and anaerobic fitness. Clearly, total fitness involves both high V02max and high anaerobic capacity. A training protocol that develops both would be a godsend.
Izumi Tabata and his colleagues at the National Institute of Fitness and Sports in Tokyo, Japan, compared the effects of moderate-intensity endurance and high-intensity intermittent training on V02max and anaerobic capacity. (Medicine and Science in Sports and Exercise (1996) 28, 1327-1330). Interestingly, the high-intensity protocol had been used by major members of the Japanese Speed Skating team for several years; it's a real-world training plan. As you will see, however, the protocol is unique among aerobic training programs for its intensity and brevity.
Many studies have been done on the effect of training on V02max, but little information has been available about the effect on anaerobic capacity. That's because until recently methods for measuring anaerobic capacity have been inadequate. This study used accumulated oxygen deficit to measure anaerobic energy release, and is one of the first to measure the effect of training on both aerobic and anaerobic capacity.
Notice that the duration of the moderate-intensity and the high-intensity protocols are drastically different: (excluding warm-ups) one hour compared to only about 4 minutes per training schedule
Tabata's moderate-intensity protocol will sound familiar; it's the same steady-state aerobic training done by many (perhaps most) fitness enthusiasts.
Here are the details (stay with me on this): In the moderate-intensity group, seven active young male physical education majors exercised on stationary bicycles 5 days per week for 6 weeks at 70% of V02max, 60 minutes each session. V02max was measured before and after the training and every week during the 6 week period. As each subject's V02max improved, exercise intensity was increased to keep them pedaling at 70% of their actual V02max. Maximal accumulated oxygen deficit was also measured, before, at 4 weeks and after the training.
A second group followed a high-intensity interval program. Seven students, also young and physically active, exercised five days per week using a training program similar to the Japanese speed skaters. After a 10-minute warm-up, the subjects did seven to eight sets of 20 seconds at 170% of V02max, with a 10 second rest between each bout. Pedaling speed was 90-rpm and sets were terminated when rpms dropped below 85. When subjects could complete more than 9 sets, exercise intensity was increased by 11 watts. The training protocol was altered one day per week. On that day, the students exercised for 30 minutes at 70% of V02max before doing 4 sets of 20 second intervals at 170% of V02max. This latter session was not continued to exhaustion. Again, V02max and anaerobic capacity was determined before, during and after the training.
In some respects the results were no surprise, but in others they may be ground breaking. The moderate-intensity endurance training program produced a significant increase in V02max (about 10%), but had no effect on anaerobic capacity. The high-intensity intermittent protocol improved V02max by about 14%; anaerobic capacity increased by a whopping 28%.
Dr. Tabata and his colleagues believe this is the first study to demonstrate an increase in both aerobic and anaerobic power. What's more, in an e-mail response to **** Winett, Dr. Tabata said, "The fact is that the rate of increase in V02max [14% for the high-intensity protocol - in only 6 weeks] is one of the highest ever reported in exercise science." (Note, the students participating in this study were members of varsity table tennis, baseball, basketball, soccer and swimming teams and already had relatively high aerobic capacities.)
The results, of course, confirm the well-known fact that the results of training are specific. The intensity in the first protocol (70% of V02max) did not stress anaerobic components (lactate production and oxygen debt) and, therefore, it was predictable that anaerobic capacity would be unchanged. On the other hand, the subjects in the high-intensity group exercised to exhaustion, and peak blood lactate levels indicated that anaerobic metabolism was being taxed to the max. So, it was probably also no big surprise that anaerobic capacity increased quite significantly.
What probably was a surprise, however, is that a 4 minute training program of very-hard 20 second repeats, in the words of the researchers, "may be optimal with respect to improving both the aerobic and the anaerobic energy release systems." That's something to write home about!
What About Fat Loss?
Angelo Tremblay, Ph.D., and his colleagues at the Physical Activities Sciences Laboratory, Laval University, Quebec, Canada, challenged the common belief among health professionals that low-intensity, long-duration exercise is the best program for fat loss. They compared the impact of moderate-intensity aerobic exercise and high-intensity aerobics on fat loss. (Metabolism (1994) Volume 43, pp.814-818)
The Canadian scientists divided 27 inactive, healthy, non-obese adults (13 men, 14 women, 18 to 32 years old) into two groups. They subjected one group to a 20-week endurance training (ET) program of uninterrupted cycling 4 or 5 times a week for 30 to 45 minutes; the intensity level began at 60% of heart rate reserve and progressed to 85%. (For a 30-year-old, this would mean starting at a heart rate of about 136 and progressing to roughly 170 bpm, which is more intense than usually prescribed for weight or fat loss.)
The other group did a 15-week program including mainly high-intensity-interval training (HIIT). Much like the ET group, they began with 30-minute sessions of continuous exercise at 70% of maximum heart rate reserve (remember, they were not accustomed to exercise), but soon progressed to 10 to 15 bouts of short (15 seconds progressing to 30 seconds) or 4 to 5 long (60 seconds progressing to 90 seconds) intervals separated by recovery periods allowing heart rate to return to 120-130 beats per minute. The intensity of the short intervals was initially fixed at 60% of the maximal work output in 10 seconds, and that of the long bouts corresponded to 70% of the individual maximum work output in 90 seconds. Intensity on both was increased 5% every three weeks.
As you might expect, the total energy cost of the ET program was substantially greater than the HIIT program. The researchers calculated that the ET group burned more than twice as many calories while exercising than the HIIT program. But (surprise, surprise) skinfold measurements showed that the HIIT group lost more subcutaneous fat. "Moreover," reported the researchers, "when the difference in the total energy cost of the program was taken into account..., the subcutaneous fat loss was ninefold greater in the HIIT program than in the ET program." In short, the HIIT group got 9 times more fat-loss benefit for every calorie burned exercising.
How can that be?
Dr. Tremblay's group took muscle biopsies and measured muscle enzyme activity to determine why high-intensity exercise produced so much more fat loss. I'll spare you the details (they are technical and hard to decipher), but this is their bottom line: "[Metabolic adaptations resulting from HIIT] may lead to a better lipid utilization in the postexercise state and thus contribute to a greater energy and lipid deficit." In other words, compared to moderate-intensity endurance exercise, high- intensity intermittent exercise causes more calories and fat to be burned following the workout. Citing animal studies, they also said it may be that appetite is suppressed more following intense intervals. (Neither group was placed on a diet.)
The next time someone pipes up about the fat-burn zone, ask them if they are familiar with the Tabata and Tremblay research reports.
[You'll find high-intensity aerobic workouts for bodybuilding in Ripped 3 and for balanced fitness, strength and endurance, in Lean For Life; both books are in the products section of this site. Routines specifically applying Tabata-type intervals are explained in chapter 5 of Challenge Yourself. Keep in mind that VO2max can only be measured in the laboratory; you'll have to estimate 170% of VO2 max. Don't try to make it too complicated. Simply chose a pace that brings you near exhaustion on the final 20-second rep; you should become more fatigued with each rep. Increase the pace as your condition improves. It's always better to underestimate your ability at the start. Begin a little slower than you think you can handle, and then adjust the pace from workout to workout. Don't attempt high-intensity intervals unless you are in good condition; they're not appropriate for beginners. Note the medical warning which follows.]
The AGAINST (from http://www.bodyrecomposition.com/fat-loss/steady-state-versus-intervals-and-epoc-practical-application.html)
Steady State vs. Intervals and EPOC: Practical Application
In the research review, Effects of exercise intensity and duration on the excess post-exercise oxygen consumption, I threw out a lot of data regarding the actual impact of exercise on the post-exercise calorie burn (called EPOC which stands for Excess Post-exercise Oxygen Consumption, essentially the ‘extra’ calories you burn after training). Since that piece was on the long side to begin with, I decided to save some more concrete examples for today’s follow-up blog.
Semi-recapping from yesterday, the paper conclude that high intensity training can generate larger EPOC’s at least in terms of the percentage contribution. The paper suggested that values of a 7% EPOC for steady state work but 14% for interval work were approximately correct values so that’s what I’m going to use.
As I mentioned yesterday, and want to look at in more detail today, although 14% sounds impressively larger than 7%, this can be terribly misleading. 7% of a large number can still be more than 14% of a much smaller number even if the percentage contribution is higher in the second case. And no matter how you cut it, the majority of calories burned come during the workout, not afterwards. As you’ll see, the EPOC doesn’t amount to jack for any realistic amount of activity.
What I want to look at today is how those values might apply in the real world in terms of determining how different types of exercise affect energy balance. This is going to be a lead in to next week’s series of articles where I make some slightly more concrete statements about the role of either intervals or steady state exercise for fat loss. Which of course leads into comments on how to practically implement either one.
Now, in the illustrations below, I’m going to be using some values that may seem pulled out of thin air; they are not and I want to describe briefly where they are coming from.
I have this sexy beast in my office for my own training; it’s a power meter bike. Yes, mine has pedals.
In addition to measuring my power output on the bike, it tells me how much total work I’ve done at the end of the ride in kilojoules; this can be converted to calories by multiplying roughly by 1. So 450 kJ expenditure is about 450 calories. Before I continue, let me explain this since anybody who knows math/physiology will realize that it’s not right.
To accurately calculate calories from kilojoules, you actually divide by 4.2 (so 420 kJ = 100 calories). Obviously it’s not one to one unless you’re one of the trainers on the Biggest Loser (bit of an in-joke there, you’d have to watch the show).
However, exercise efficiency while cycling varies from 20-25%, meaning that only that much of the actual caloric expenditure goes into power output. The rest is lost as heat.
So to figure total calories burned you re-divide by anywhere from 4 to 5 (depending on efficiency). If you assume 25% efficiency, you re-divide by 4. Essentially you divide kJ by 4 and then multiply back by 4. So you end up being able to roughly estimate calorie burn by simply taking kJ as the calorie burn at a 1:1 ratio. Ok, back to the article.
As well, I’ve checked the value on the powerbike using the Bodybugg (the little armband thingie that estimates energy expenditure based on body heat, movement and a couple of other things).
I’ve also recently checked the bike against the caloric expenditure from my new Polar RS800 watch and it is basically identical to the powerbike’s kJ reading with the Bugg being in close shooting distance of both (the value isn’t identical). My point being that the values I’m going to use, I consider accurate. I’m not making them up so that my math will support what I’m trying to argue.
Now, semi-tangentially, a lot of people on my forum have been using the Bugg and one thing that keeps coming up (so I might as well address it) is disappointment that an interval workout invariably ends up burning either about the same or less total calories than a similar amount of moderate steady state.
That is to say that 30 minutes of intervals may burn roughly 300 calories. But so does 30 minutes of moderate intensity cardio (for trained folks). And the intervals are a hell of a lot tougher.
How does that make sense?
The reason of course is that the interval workout is alternating between very high caloric expenditures and very low expenditures such that the average expenditure still ends up coming out about the same. That is, say I do 1 minute intervals with 1 minute rest, alternating between 15 cal/min during the hard bit and 5 cal/min during the recovery. That’s an average of 10 cal/min. I can achieve that same 10 cal/min consistently with moderate intensity cardio. The second workout will be far easier to complete.
So if there’s a huge benefit to intervals, one place it might come is from the EPOC (note: there are other potential benefits of intervals that I’ll be addressing in future blog posts).
So I’m going to be focusing ONLY on EPOC here. Again, I’m going to assume a 7% EPOC for steady state cardio and a 14% EPOC for intervals and put those into some real world perspective.
Say I do 20 minutes of intervals and burn 200 calories. I get a 14% EPOC which is 28 whole calories. Total calorie burn = 228 calories.
Let’s say I do 20 minutes of steady state cardio and burn the same 200 calories. 7% EPOC which is 14 calories = 214 calories.
So, for an equivalent duration workout, the interval workout comes out a whopping 14 calories ahead due to the impact of EPOC. That will net me an extra pound of fat loss every 250 days (3500 calories / 14 calories per day = 250 days). Hooray. Clearly, for any equivalent length workout the interval training will always come out slightly ahead.
Except that you wouldn’t expect someone to do longer and and longer and longer interval workouts; the whole point of intervals (or one point) is that they are more time efficient, that you get all you need in somewhere between 4 and 20-30 minutes (depending on which expert you’re listening to and what they’re selling).
So it’s more useful to compare that 20 minute interval workout to longer steady state workouts which is what most would do in the real world.
Here are calculations for different length steady state workouts based on an average burn of 10 cal/min and a 7% EPOC.
30 minutes = 300 calories + 7% EPOC = 21 calories = 321 calories.
40 minutes = 400 calories + 7% EPOC = 28 calories = 428 calories.
50 minutes = 500 calories + 7% EPOC = 35 calories = 535 calories.
60 minutes = 600 calories + 7% EPOC = 42 calories = 642 calories.
Now lemme be generous and assume I’m doing 30 minutes of intervals with a 14% EPOC
30 minute interval session = 300 calories + 14% EPOC = 42 calories = 342 calories.
While this is certainly a few more (21) calories than the 30 minute steady state session, it pales in comparison to the longer sessions. Sixty minutes of steady state cardio burns 642 calories, compared to 342 from the interval training. Looking purely at energy balance (and, again, there are other issues to consider) and fat loss, which will get me lean faster?
But you say, I don’t have time to do an hour of cardio, I get bored doing cardio, etc, etc. Those are practical considerations (which are, of course, important), not physiological ones and I’ll be coming back to those in next week’s continuation of the series. Purely physiologically speaking, the EPOC argument just doesn’t hold up. Not only is the EPOC from any realistic amount of intervals or steady state cardio irrelevant, short interval sessions still burn far LESS calories than longer steady state sessions.
The intervals only come out a TINY bit ahead if you compare workouts of identical length and even there the difference is absolutely insignificant.
But between now and Monday, here’s a question for my readers (or the pro-interval crowd) to ponder:
Let’s say I want or need to train daily for fat loss (most athletes train every day, as do most dieters).
Which am I more likely to do on a day-in day-out basis? Which is more likely to lean me out faster? Which am I more likely to BE ABLE to do daily (from a recovery standpoint)?
30 minutes of intervals: burning 342 calories including EPOC.
60 minutes of moderate teady state cardio: burning 642 calories including EPOC.
Note: Yes, I’m making it sound like it’s an either/or choice here which it’s clearly not. But just consider that one issue in isolation for now.
Note again: I’d note again that this series of articles is absolutely NOT meant to be against interval training as one tool in the fat loss arsenal. My issue is simply with the uncritical claim being made that intervals are always superior to steady state (or that steady state is somehow detrimental to fat loss) as well as some of the arguments being made to support the contention that interval training is any of these things.
Next up in the series, Steady State vs. Intervals: Explaining the Disconnect Part 1
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So what do you think? It seems to me there must be some distinction the body makes between 200 calories burned walking and 200 calories burned during insanity because of how spent the latter leaves me...
FOR HIIT (from http://www.cbass.com/FATBURN.HTM)
From The Desk of Clarence Bass
FORGET THE FAT-BURN ZONE
High Intensity Aerobics Amazingly Effective
"The rate of increase in V02max is one of the highest ever reported."
Izumi Tabata, Japan
"Fat burn is greater when exercise intensity is high." Metabolism
I believe in high-intensity aerobics. In Ripped 3, for bodybuilders, I recommended "a variety of relatively short and infrequent aerobic sessions interspersed with explosive muscular effort." In Lean For Life, published six years later, I emphasized high-intensity aerobics even more; I reduced the frequency of aerobic sessions to two times a week (in Ripped 3 I recommended up to four) and substantially increased the intensity. But it wasn't until recently, when my friend Richard Winett, Ph.D., publisher of Master Trainer, called my attention to new research findings, that I came to fully appreciate the superiority of high intensity aerobics compared to the usual prescription that heart rate be maintained between 60% and 80% of maximum.
As explained in the nearby FAQ (Low intensity aerobics?), high intensity aerobics burns the same amount of fat as low intensity, but the expenditure of calories is substantially greater; plus, intense aerobics produces a higher level of fitness. Importantly, the more fit you become, the more likely you are to use fat as fuel for any given activity. And now, research in Japan and in Canada shows that short, very intense aerobic sessions are amazingly effective for both fitness and fat loss.
Maximal oxygen uptake, or V02max, is generally regarded as the best single measure of aerobic fitness. As the rate of exercise increases, your body eventually reaches a limit for oxygen consumption. This limit is the peak of your aerobic capacity, or your V02max. As intensity increases beyond V02max, your body must shift to anaerobic (without oxygen) energy production. An oxygen debt begins to build at this point and blood lactate levels climb. In general terms, one's ability to continue exercising in the face of rising oxygen deficit and lactate levels is called anaerobic capacity.
This is important because many high-intensity sports (including basketball, football, soccer and speed skating) require a high level of both aerobic and anaerobic fitness. Clearly, total fitness involves both high V02max and high anaerobic capacity. A training protocol that develops both would be a godsend.
Izumi Tabata and his colleagues at the National Institute of Fitness and Sports in Tokyo, Japan, compared the effects of moderate-intensity endurance and high-intensity intermittent training on V02max and anaerobic capacity. (Medicine and Science in Sports and Exercise (1996) 28, 1327-1330). Interestingly, the high-intensity protocol had been used by major members of the Japanese Speed Skating team for several years; it's a real-world training plan. As you will see, however, the protocol is unique among aerobic training programs for its intensity and brevity.
Many studies have been done on the effect of training on V02max, but little information has been available about the effect on anaerobic capacity. That's because until recently methods for measuring anaerobic capacity have been inadequate. This study used accumulated oxygen deficit to measure anaerobic energy release, and is one of the first to measure the effect of training on both aerobic and anaerobic capacity.
Notice that the duration of the moderate-intensity and the high-intensity protocols are drastically different: (excluding warm-ups) one hour compared to only about 4 minutes per training schedule
Tabata's moderate-intensity protocol will sound familiar; it's the same steady-state aerobic training done by many (perhaps most) fitness enthusiasts.
Here are the details (stay with me on this): In the moderate-intensity group, seven active young male physical education majors exercised on stationary bicycles 5 days per week for 6 weeks at 70% of V02max, 60 minutes each session. V02max was measured before and after the training and every week during the 6 week period. As each subject's V02max improved, exercise intensity was increased to keep them pedaling at 70% of their actual V02max. Maximal accumulated oxygen deficit was also measured, before, at 4 weeks and after the training.
A second group followed a high-intensity interval program. Seven students, also young and physically active, exercised five days per week using a training program similar to the Japanese speed skaters. After a 10-minute warm-up, the subjects did seven to eight sets of 20 seconds at 170% of V02max, with a 10 second rest between each bout. Pedaling speed was 90-rpm and sets were terminated when rpms dropped below 85. When subjects could complete more than 9 sets, exercise intensity was increased by 11 watts. The training protocol was altered one day per week. On that day, the students exercised for 30 minutes at 70% of V02max before doing 4 sets of 20 second intervals at 170% of V02max. This latter session was not continued to exhaustion. Again, V02max and anaerobic capacity was determined before, during and after the training.
In some respects the results were no surprise, but in others they may be ground breaking. The moderate-intensity endurance training program produced a significant increase in V02max (about 10%), but had no effect on anaerobic capacity. The high-intensity intermittent protocol improved V02max by about 14%; anaerobic capacity increased by a whopping 28%.
Dr. Tabata and his colleagues believe this is the first study to demonstrate an increase in both aerobic and anaerobic power. What's more, in an e-mail response to **** Winett, Dr. Tabata said, "The fact is that the rate of increase in V02max [14% for the high-intensity protocol - in only 6 weeks] is one of the highest ever reported in exercise science." (Note, the students participating in this study were members of varsity table tennis, baseball, basketball, soccer and swimming teams and already had relatively high aerobic capacities.)
The results, of course, confirm the well-known fact that the results of training are specific. The intensity in the first protocol (70% of V02max) did not stress anaerobic components (lactate production and oxygen debt) and, therefore, it was predictable that anaerobic capacity would be unchanged. On the other hand, the subjects in the high-intensity group exercised to exhaustion, and peak blood lactate levels indicated that anaerobic metabolism was being taxed to the max. So, it was probably also no big surprise that anaerobic capacity increased quite significantly.
What probably was a surprise, however, is that a 4 minute training program of very-hard 20 second repeats, in the words of the researchers, "may be optimal with respect to improving both the aerobic and the anaerobic energy release systems." That's something to write home about!
What About Fat Loss?
Angelo Tremblay, Ph.D., and his colleagues at the Physical Activities Sciences Laboratory, Laval University, Quebec, Canada, challenged the common belief among health professionals that low-intensity, long-duration exercise is the best program for fat loss. They compared the impact of moderate-intensity aerobic exercise and high-intensity aerobics on fat loss. (Metabolism (1994) Volume 43, pp.814-818)
The Canadian scientists divided 27 inactive, healthy, non-obese adults (13 men, 14 women, 18 to 32 years old) into two groups. They subjected one group to a 20-week endurance training (ET) program of uninterrupted cycling 4 or 5 times a week for 30 to 45 minutes; the intensity level began at 60% of heart rate reserve and progressed to 85%. (For a 30-year-old, this would mean starting at a heart rate of about 136 and progressing to roughly 170 bpm, which is more intense than usually prescribed for weight or fat loss.)
The other group did a 15-week program including mainly high-intensity-interval training (HIIT). Much like the ET group, they began with 30-minute sessions of continuous exercise at 70% of maximum heart rate reserve (remember, they were not accustomed to exercise), but soon progressed to 10 to 15 bouts of short (15 seconds progressing to 30 seconds) or 4 to 5 long (60 seconds progressing to 90 seconds) intervals separated by recovery periods allowing heart rate to return to 120-130 beats per minute. The intensity of the short intervals was initially fixed at 60% of the maximal work output in 10 seconds, and that of the long bouts corresponded to 70% of the individual maximum work output in 90 seconds. Intensity on both was increased 5% every three weeks.
As you might expect, the total energy cost of the ET program was substantially greater than the HIIT program. The researchers calculated that the ET group burned more than twice as many calories while exercising than the HIIT program. But (surprise, surprise) skinfold measurements showed that the HIIT group lost more subcutaneous fat. "Moreover," reported the researchers, "when the difference in the total energy cost of the program was taken into account..., the subcutaneous fat loss was ninefold greater in the HIIT program than in the ET program." In short, the HIIT group got 9 times more fat-loss benefit for every calorie burned exercising.
How can that be?
Dr. Tremblay's group took muscle biopsies and measured muscle enzyme activity to determine why high-intensity exercise produced so much more fat loss. I'll spare you the details (they are technical and hard to decipher), but this is their bottom line: "[Metabolic adaptations resulting from HIIT] may lead to a better lipid utilization in the postexercise state and thus contribute to a greater energy and lipid deficit." In other words, compared to moderate-intensity endurance exercise, high- intensity intermittent exercise causes more calories and fat to be burned following the workout. Citing animal studies, they also said it may be that appetite is suppressed more following intense intervals. (Neither group was placed on a diet.)
The next time someone pipes up about the fat-burn zone, ask them if they are familiar with the Tabata and Tremblay research reports.
[You'll find high-intensity aerobic workouts for bodybuilding in Ripped 3 and for balanced fitness, strength and endurance, in Lean For Life; both books are in the products section of this site. Routines specifically applying Tabata-type intervals are explained in chapter 5 of Challenge Yourself. Keep in mind that VO2max can only be measured in the laboratory; you'll have to estimate 170% of VO2 max. Don't try to make it too complicated. Simply chose a pace that brings you near exhaustion on the final 20-second rep; you should become more fatigued with each rep. Increase the pace as your condition improves. It's always better to underestimate your ability at the start. Begin a little slower than you think you can handle, and then adjust the pace from workout to workout. Don't attempt high-intensity intervals unless you are in good condition; they're not appropriate for beginners. Note the medical warning which follows.]
The AGAINST (from http://www.bodyrecomposition.com/fat-loss/steady-state-versus-intervals-and-epoc-practical-application.html)
Steady State vs. Intervals and EPOC: Practical Application
In the research review, Effects of exercise intensity and duration on the excess post-exercise oxygen consumption, I threw out a lot of data regarding the actual impact of exercise on the post-exercise calorie burn (called EPOC which stands for Excess Post-exercise Oxygen Consumption, essentially the ‘extra’ calories you burn after training). Since that piece was on the long side to begin with, I decided to save some more concrete examples for today’s follow-up blog.
Semi-recapping from yesterday, the paper conclude that high intensity training can generate larger EPOC’s at least in terms of the percentage contribution. The paper suggested that values of a 7% EPOC for steady state work but 14% for interval work were approximately correct values so that’s what I’m going to use.
As I mentioned yesterday, and want to look at in more detail today, although 14% sounds impressively larger than 7%, this can be terribly misleading. 7% of a large number can still be more than 14% of a much smaller number even if the percentage contribution is higher in the second case. And no matter how you cut it, the majority of calories burned come during the workout, not afterwards. As you’ll see, the EPOC doesn’t amount to jack for any realistic amount of activity.
What I want to look at today is how those values might apply in the real world in terms of determining how different types of exercise affect energy balance. This is going to be a lead in to next week’s series of articles where I make some slightly more concrete statements about the role of either intervals or steady state exercise for fat loss. Which of course leads into comments on how to practically implement either one.
Now, in the illustrations below, I’m going to be using some values that may seem pulled out of thin air; they are not and I want to describe briefly where they are coming from.
I have this sexy beast in my office for my own training; it’s a power meter bike. Yes, mine has pedals.
In addition to measuring my power output on the bike, it tells me how much total work I’ve done at the end of the ride in kilojoules; this can be converted to calories by multiplying roughly by 1. So 450 kJ expenditure is about 450 calories. Before I continue, let me explain this since anybody who knows math/physiology will realize that it’s not right.
To accurately calculate calories from kilojoules, you actually divide by 4.2 (so 420 kJ = 100 calories). Obviously it’s not one to one unless you’re one of the trainers on the Biggest Loser (bit of an in-joke there, you’d have to watch the show).
However, exercise efficiency while cycling varies from 20-25%, meaning that only that much of the actual caloric expenditure goes into power output. The rest is lost as heat.
So to figure total calories burned you re-divide by anywhere from 4 to 5 (depending on efficiency). If you assume 25% efficiency, you re-divide by 4. Essentially you divide kJ by 4 and then multiply back by 4. So you end up being able to roughly estimate calorie burn by simply taking kJ as the calorie burn at a 1:1 ratio. Ok, back to the article.
As well, I’ve checked the value on the powerbike using the Bodybugg (the little armband thingie that estimates energy expenditure based on body heat, movement and a couple of other things).
I’ve also recently checked the bike against the caloric expenditure from my new Polar RS800 watch and it is basically identical to the powerbike’s kJ reading with the Bugg being in close shooting distance of both (the value isn’t identical). My point being that the values I’m going to use, I consider accurate. I’m not making them up so that my math will support what I’m trying to argue.
Now, semi-tangentially, a lot of people on my forum have been using the Bugg and one thing that keeps coming up (so I might as well address it) is disappointment that an interval workout invariably ends up burning either about the same or less total calories than a similar amount of moderate steady state.
That is to say that 30 minutes of intervals may burn roughly 300 calories. But so does 30 minutes of moderate intensity cardio (for trained folks). And the intervals are a hell of a lot tougher.
How does that make sense?
The reason of course is that the interval workout is alternating between very high caloric expenditures and very low expenditures such that the average expenditure still ends up coming out about the same. That is, say I do 1 minute intervals with 1 minute rest, alternating between 15 cal/min during the hard bit and 5 cal/min during the recovery. That’s an average of 10 cal/min. I can achieve that same 10 cal/min consistently with moderate intensity cardio. The second workout will be far easier to complete.
So if there’s a huge benefit to intervals, one place it might come is from the EPOC (note: there are other potential benefits of intervals that I’ll be addressing in future blog posts).
So I’m going to be focusing ONLY on EPOC here. Again, I’m going to assume a 7% EPOC for steady state cardio and a 14% EPOC for intervals and put those into some real world perspective.
Say I do 20 minutes of intervals and burn 200 calories. I get a 14% EPOC which is 28 whole calories. Total calorie burn = 228 calories.
Let’s say I do 20 minutes of steady state cardio and burn the same 200 calories. 7% EPOC which is 14 calories = 214 calories.
So, for an equivalent duration workout, the interval workout comes out a whopping 14 calories ahead due to the impact of EPOC. That will net me an extra pound of fat loss every 250 days (3500 calories / 14 calories per day = 250 days). Hooray. Clearly, for any equivalent length workout the interval training will always come out slightly ahead.
Except that you wouldn’t expect someone to do longer and and longer and longer interval workouts; the whole point of intervals (or one point) is that they are more time efficient, that you get all you need in somewhere between 4 and 20-30 minutes (depending on which expert you’re listening to and what they’re selling).
So it’s more useful to compare that 20 minute interval workout to longer steady state workouts which is what most would do in the real world.
Here are calculations for different length steady state workouts based on an average burn of 10 cal/min and a 7% EPOC.
30 minutes = 300 calories + 7% EPOC = 21 calories = 321 calories.
40 minutes = 400 calories + 7% EPOC = 28 calories = 428 calories.
50 minutes = 500 calories + 7% EPOC = 35 calories = 535 calories.
60 minutes = 600 calories + 7% EPOC = 42 calories = 642 calories.
Now lemme be generous and assume I’m doing 30 minutes of intervals with a 14% EPOC
30 minute interval session = 300 calories + 14% EPOC = 42 calories = 342 calories.
While this is certainly a few more (21) calories than the 30 minute steady state session, it pales in comparison to the longer sessions. Sixty minutes of steady state cardio burns 642 calories, compared to 342 from the interval training. Looking purely at energy balance (and, again, there are other issues to consider) and fat loss, which will get me lean faster?
But you say, I don’t have time to do an hour of cardio, I get bored doing cardio, etc, etc. Those are practical considerations (which are, of course, important), not physiological ones and I’ll be coming back to those in next week’s continuation of the series. Purely physiologically speaking, the EPOC argument just doesn’t hold up. Not only is the EPOC from any realistic amount of intervals or steady state cardio irrelevant, short interval sessions still burn far LESS calories than longer steady state sessions.
The intervals only come out a TINY bit ahead if you compare workouts of identical length and even there the difference is absolutely insignificant.
But between now and Monday, here’s a question for my readers (or the pro-interval crowd) to ponder:
Let’s say I want or need to train daily for fat loss (most athletes train every day, as do most dieters).
Which am I more likely to do on a day-in day-out basis? Which is more likely to lean me out faster? Which am I more likely to BE ABLE to do daily (from a recovery standpoint)?
30 minutes of intervals: burning 342 calories including EPOC.
60 minutes of moderate teady state cardio: burning 642 calories including EPOC.
Note: Yes, I’m making it sound like it’s an either/or choice here which it’s clearly not. But just consider that one issue in isolation for now.
Note again: I’d note again that this series of articles is absolutely NOT meant to be against interval training as one tool in the fat loss arsenal. My issue is simply with the uncritical claim being made that intervals are always superior to steady state (or that steady state is somehow detrimental to fat loss) as well as some of the arguments being made to support the contention that interval training is any of these things.
Next up in the series, Steady State vs. Intervals: Explaining the Disconnect Part 1
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Well I did not read everything in your post but I will give my 2 cents worth. I love HIIT because I have more energy and my endurance is much longer than when I was only doing lower impact exercising. The interval part of it makes your heart rate go up and down much faster which fuels your metabolism and makes you breath much deeper therefore giving you a more intense workout and the HIIT workout last up to 48 hours of burning fat. That is why I shred so much more fat in 60 days of Insanity than when I do 90 days of P90X. I love both workout programs and have had great results from both. HIIT workouts are for people who are some what healthy already but looking to really push past the norm and become super fit.0
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Not sure whereyour calcs came from but I burn about 12 cals per minute doing steady state while I burn about 15 cals/min on average during HIIT. So 30 min steady state = 360 while I only need to do intervals for 24 minutes to get the same caloric burn, but HIIT also has a higher EPOC so that amount of time would be reduced even further.
It all depends on you. I do it on the treadmill and run at 11 mph for 45 sec followed by 1 min at 6.5 mph whereas I do steady state at 8.0mph. My HIIT speed averages 8.3-8.5mph.
Again it depends on how hard you are pushing yourself from one type of training to the other, not necessarly the type of training itself.0 -
I think a good portion of your decision in which to choose has to do with how you want to look "nekkid" as well LOL! HIIT stimulates the fast twitch muscle fibers which we know are the most important ones when one wants to add new muscle whereas steady state cardio stimulates the slow twitch muscle fibers which are great for endurance but do nothing for your physical appearance. If you just want to run/walk/elliptical longer just for the sake of running/walking/elliticaling (not a word lol) longer and are only concerned with burning calories period then steady state would be your best bet. If you want to tightest, leanest, sexiest physique with curves in all the right places, the HIIT is your BFF alongside a good resistance program.
Excuse any typos, this print is really tiny and I don't feel like proofing LOL!0 -
That was just an example of working out longer to burn the same calories. I am a woman, so probably lighter than you at 119lbs. I burn about 9 calories/min doing steady state at 80% of my mhr and 11/min doing hiit with my average hr at 90%. I can't physically work much harder than that with the hiit but still only burn 215 calories in 20 minutes whereas I could spend 30-40 mins and burn the same cals. The against author argues that epoc is only like 10% more, whereas the for author says hiit preferentially burns fat, which seems to be the best argument for doing it.0
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